Abstract

Frequency distribution according to plant size as measured by dimensional analysis on different mathematical bases were determined for 10 common perennial plant species from Rock Valley in the northern Mojave Desert in Nevada. A total of 4282 individual plants was measured. The data provide information concerning the stability and prosperity of the natural vegetation as judged by the relative proportions of individuals in the size-class spectrum, as well as show graphically the relative abundance of the different species in the study area. On the species level, the populations were close to normally distributed on the loge basis, but with remarkably negative skewness due to better segregation of the small-sized individuals into many segmental units. On the arithmetic basis, three categories of frequency pattern were recognized, but all with marked positive skewness due to better segregation of large-sized individuals into many segmental units. The feature common to all species studied is the preponderance of young individuals, which in many cases could have an abundance many times that of large individuals. The natural vegetation in Rock Valley, therefore, represents a reasonably active stage.